The present invention relates generally to methods and apparatus for preparing firearm cartridges and, more particularly, for trimming reusable cases in preparation for reloading of cases to create additional cartridges.
A wide variety of firearm cartridges are known, each type sized according to the firearm it is used with. In general, however, each such cartridge comprises a case having an open end, propellant inserted within the case (such as gunpowder), a bullet inserted within and often protruding from the open end of the case. A primer is often attached to the case at the end opposite the bullet. In use, the primer is struck by a firing pin and ignites the propellant to force the bullet out of the case and from the firearm toward the target. As that happens, the explosive forces typically change the shape of the case somewhat, fire forming it radially to the dimensions of the firearm chamber and extending or lengthening it longitudinally.
It has been found to be particularly advantageous to reload spent cases with primer, propellant and bullet and reuse the additional cartridge with the same firearm. For example, since commercially produced firearms of a given type have some minute differences in cartridge chamber dimensions, commercially produced cartridges must be sized slightly small in order to be usable in all such firearms. Unfortunately, sizing the cartridge in that manner produces combustion inefficiencies and variances in firearm operating characteristics. However, spent cases from a given firearm have been fire formed to the specific firearm chamber dimensions. When reused, explosive force previously expended to radially expand the case is then available to increase the longitudinal force on the bullet.
In order to reuse the case in an efficient and safe manner, the excess longitudinal dimension of the case caused by the previous use must be trimmed off. Various prior devices and methods are known for achieving that trimming. In general, the case was secured within a chuck or collet by clamping the case about its diameter with the open end of the case protruding. Since each size or caliber of cartridge employed a case having a different diameter, such chucks were either adjustable to create differently sized openings to receive a variety of cases or substitutable into the device, with specific chucks for specific sized cases. Prior trimming devices also included a rotatable cutting tool aligned on a stand opposite the chuck opening and movable longitudinally toward the open end of the case. The overall configuration resembled a small lathe.
The cutting edge of the cutting tool was typically exposed to the user, and different sized cases often required the use of different removable pilot pieces inserted into the cutting tool adjacent the cutting edge to ensure proper alignment. Also, many such prior devices did not confine the shavings from the trimming process, instead allowing shavings to fall away from the cutting edge and onto the stand supporting the trimming components or the surface or floor supporting the stand. Rotation of the cutting tool was accomplished manually or by connection to a rotary power source.
Accordingly, it is an object of the present invention to provide an improved method and apparatus for trimming firearm cases. Further objects include the provision of a case trimming apparatus which:
a. is more compact and less costly to manufacture, PA1 b. more easily and reliably aligns the case with the cutting tool, PA1 c. is safer and cleaner to use, PA1 d. accommodates a wider variety of case sizes with fewer specialized parts, and PA1 e. is adaptable to either manual or power driven actuation.
These and other objects of the present invention are attained by the provision of a case trimming apparatus having a hollow, longitudinally extending housing which is open at both ends, receiving and securing a cutting tool at one end and enclosing the cutting edge of that tool while rotatably receiving the open end of a case at its other end and retaining the case in alignment with the cutting edge. The end of the housing which receives the open end of the case includes a ledge to engage the shoulder of the case rather than engage the case by its diameter. The ledge can be removably mounted in the housing. The housing includes a chamber for retaining shavings and may include an opening from that chamber to remove shavings during trimming. Manual actuation is accomplished by rotation of the case relative to the housing while applying pressure to the case toward the cutting edge. An adapter is provided for connecting the housing to a standard power tool, such as a conventional electric hand drill, in order to provide an alternative rotary power source.
Additional objects, advantages and novel features of the present invention will become readily apparent to those skilled in the art from the following drawings and detailed description of preferred embodiments.